The present invention relates to an axial-flow fan, particularly to a small fan which is axially compact, with a scroll plate or housing surrounding the impeller and whose inner contour has a cylindrical configuration in the vicinity of the axial median plane and extends both towards the inlet side and the outlet side in a polygonal, particularly square profile describing the impeller diameter and accompanied by the formation of corner areas, and with a central, coaxial core formed by the drive motor, the impeller hub and the mounting flange for the drive motor, whereby the core has a surface conically tapering towards the inlet side.
Such axial-flow fans are used in a preferred manner for cooling electrical and electronic equipment and installations, particularly where very compact fan dimensions and low noise with high air output are required. The dimensions of the fans which can be used in such devices are limited by the available structural space. Thus, it is not possible to increase the dimensions in order to increase the output of such fans.
An axial-flow fan of the aforementioned type is known (DOS No. 29 40 650), in which relatively high air outputs are obtained in that on the inlet side the impeller hub is provided with a ring surface conically tapering towards the end face. The scroll plate is cylindrical in the vicinity of the axial median plane while leaving a small gap to the fan blades and widens to a square shape by walls sloping in the corner areas both towards the inlet side and towards the outlet side and extending symmetrically to the axial median plane.
Due to the fact that in the equipment in question, ever-smaller electrical and/or electronic components are being increasingly used, the casings or housings of such equipment can also be made ever-smaller. This means for the small fans of the type considered herein that the efficiency is limited by the opposing dynamic pressures in the installation areas.